In order to measure the analyte concentration, for example, the blood glucose concentration (the blood glucose level), in a blood sample, a portable biosensor system is used that includes a measuring instrument with an operation part and a sensor chip that is insertable into and removable from the measuring instrument.
The concentration of an analyte is calculated based on the amount of an oxidant or a reductant that is generated by an enzyme cycling reaction. The reaction is carried out through an oxidoreductase, with the analyte used as a substrate. The rate of the enzyme cycling reaction depends on the temperature (the reaction temperature) at which the reaction is carried out. Therefore, it is desirable to correct the analyte concentration based on the reaction temperature.
As described in, for example, JP 2003-156469 A, the reaction temperature is measured with a temperature sensor disposed in the measuring instrument. In the biosensor system described in JP 2003-156469 A, however, since the internal temperature of the measuring instrument is measured, the reaction temperature measured therein does not reflect the temperature of the blood sample accurately. Accordingly, an error may be caused in the measurement of the analyte concentration.
JP 2001-235444 A, JP 2003-42995 A, and International Publication WO2003/062812 each disclose a biosensor system for improving the accuracy of measuring the reaction temperature. The biosensor systems described in JP 2001-235444 A and JP 2003-42995 A each include a thermally-conductive member in the vicinity of a blood sample holding part of a sensor chip and detect the temperature of the blood sample transmitted through the thermally-conductive member by a temperature sensor disposed in the measuring instrument. In the biosensor systems described in JP 2001-235444 A and JP 2003-42995 A, since a resin plate is disposed between the thermally-conductive member and the blood sample holding part, the thermally-conductive member does not come into contact with a blood sample. In the biosensor system described in International Publication WO2003/062812, a temperature sensor and a thermally-conductive member are disposed in the insertion part of the measuring instrument where a sensor chip is inserted and the temperature of the blood sample is transmitted to the temperature sensor through the thermally-conductive member.